Homebrew PCBs

Try a regular good flash light or a halogen desk lamp.  It works
surprisingly well.

A related trick if this method is used is to not use two identical targets
as is normally done.  Instead use complimentary targets.  For example, on
one layer use concentric circles of 5 mil lines and 5 mil spacing.  On the
other layer use the same dimensions but start with a space and then a black
line.  In other words, you will have a positive and a negative target.
  When placed on top of each other and viewed with light from below they
will turn all black only when perfectly aligned.  Any error is very obvious.

Another comment:
Taping just a hinge allows a slight movement of the layers since the hinge
allows a microscopic movement.  Cut off the corners of the top layer where
the hinge will normally be placed. Placing tape on those corners really
locks the artwork together without any movement.

Finally, place two half thickness spacers one on each side of the tail to
force it to be in the center when the board is put under the glass for
exposure. For ironing use just one half sized spacer on the bottom and push
the tail down on it to keep the top and bottom aligned.
Bertho
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From: Philip Pemberton  Sent: Sunday, July 06, 2008 03:45

Bertho Boman wrote:
> Why blind alignment? Crank up enough backlight and you should be able to
> see through the paper.

Perhaps a strobe light would be powerful enough. Assuming you could get used

to the flickering :)